Field of the Invention
The present invention relates to wireless communication, and more particularly, to a method of transmitting a signal in a wireless communication system including a relay station.
Discussion of the Related Art
In ITU-R (International Telecommunication Union Radio communication sector), a standardization task for IMT (International Mobile Telecommunication)-Advanced (i.e., the next-generation mobile communication system after the 3rd generation) is being in progress. IMT-Advanced sets its goal to support IP (Internet Protocol)-based multimedia service at the data transfer rate of 1 Gbps in the stop and slow-speed moving states and at the data transfer rate of 100 Mbps in the fast-speed moving state.
3GPP (3rd Generation Partnership Project) is a system standard to satisfy the requirements of IMT-Advanced, and it is preparing for LTE-Advanced improved from LTE (Long Term Evolution) based on OFDMA (Orthogonal Frequency Division Multiple Access)/SC-FDMA (Single Carrier-Frequency Division Multiple Access) transmission schemes. LTE-Advanced is one of the strong candidates for IMT-Advanced. Relay station technology is included in the major technology of LTE-Advanced.
A relay station is an apparatus for relaying signals between a base station and a user equipment and is used to extend the cell coverage of a wireless communication system and improve the throughput.
In a wireless communication system including a relay station, a lot of researches are being carried out on a method of transmitting a signal between a base station and the relay station. To use a conventional method of transmitting a signal between a base station and a mobile station in transmitting a signal between a base station and a relay station without change is problematic.
In the conventional method of transmitting a signal between a base station and a mobile station, in general, the mobile station transmits a signal over the one entire subframe when viewed from the time domain. One of the reasons why the mobile station transmits a signal over the one entire subframe is to set the duration time of each channel through which the signal is transmitted as long as possible in order to reduce the maximum instant power consumed by the mobile station.
However, a relay station may not frequently transmit or receive a signal over the entire one subframe when viewed from the time domain. A relay station experiences the frequent switching of a reception mode and a transmission mode because it relays signals for a plurality of mobile stations. There is a need for a specific time period (hereinafter called a guard time) for which the relay station does not transmit or receive a signal in order to prevent interference between signals and stabilize the operation between the reception mode period and the transmission mode period when the reception mode and the transmission mode are switched.
Unlike a mobile station, a relay station may not transmit or receive a signal over the one entire subframe owing to the guard time. Accordingly, the conventional method of transmitting a signal between a base station and a mobile station cannot be used without change.
Furthermore, since a relay station has fewer power restrictions as compared with a mobile station and typically has an excellent channel state with a base station, the conventional method of transmitting a signal between a base station and a mobile station needs not to be used to transmit a signal between a base station and a relay station without change.
There is a need for a new method of transmitting a signal in a wireless communication system including a relay station.